Day 4 of Aberdeen, SD (KABR)

Surprisingly, even with almost no wind, it still didn’t cool down much after 2 AM, with a low of -21F. Really mysterious! Full sunshine and a moderating air mass led to a rapid warmup to a high of 12-13F this afternoon, with some southerly to easterly wind with only relatively light winds so far but the maximum wind will occur this evening. Southerly winds and warm advection will inhibit radiational cooling tonight even with clear skies, with no cooling expected after 06z and therefore the low at the beginning (Friday 06z) after only modest cooling in the evening. USL and NWS seem too cold given it's already 12-13F this afternoon and the increasing southerly wind and warm advection doesn't bode well for much cooling.

 

Temperatures will rapidly warm tomorrow with sunshine, continued warm advection, and southerly winds gradually turning to a west-southwesterly wind with a downslope component. Also, there is a snow cover gradient with bare ground not far to the southwest, and a west-southwesterly wind would advect air warmed over the bare ground into Aberdeen, though the winds will be gradually weakening during the day tomorrow as well and might not be strong enough to produce the full warming effect. Interestingly, while the HRRR has been too cold for the high lately, it is actually warmer than other models for tomorrow, perhaps due to slightly overadvection of air warmed by the bare ground to the southwest. Still, with the sunshine and downsloping wind, I expect the high to be warmer than most model guidance. The maximum wind will likely occur tomorrow morning as the sunshine initially helps mix stronger winds aloft down to the surface before the pressure gradient and resulting winds weaken in the afternoon.

 

Source: PivotalWeather